Theoretical and experimental studies on the activation of ethylsilane by bare Co+ cations

The potential-energy surface for the activation of ethylsilane by "naked" Co+ ions is investigated by using density functional theory at the B3LYP level of theory and a valence double zeta basis. In particular, the pathways for the expulsion of the neutral molecules SiH4, H-2, and CH4 are examined, which are also observed in the mass spectrometric experiments. Five conceivable oxidative additions of the substrate to Co+ are considered in the computational study, i.e. the primary insertions of the metal ion into the C-Si, C(1)-H, C(2)-H, C-C, and Si-H bonds. Comparison with experimental data shows qualitative agreement in that all experimentally observed products are predicted by theory to be formed in exothermic reactions with thermally surmountable barriers. Quantitatively, the ratio of the losses of SiH4, H-2, and CH4 is less well reproduced by the applied theoretical approach; however, the energetic differences between the rate determining transition states are too small to be resolved within the accuracy of most, if not all, nowadays theoretical methods applicable to transition-metal compounds. (Int J Mass Spectrom 199 (2000) 107-125) (C) 2000 Elsevier Science B.V.